It is desirable to reduce acoustic noise which occurs as a byproduct of operating heating or cooling systems, such as heating, ventilating and air conditioning (HVAC) systems or refrigeration systems. A substantial amount of the acoustic noise associated with the circulation of air in such systems, e.g., for the operation of a fan of the system. Typical means of fan noise reduction are accomplished with the design of efficient fan systems that produce high airflow with minimal fan speeds.